Police in Miami have shot dead a man who was chewing the face of another man.

Officers were called around 2pm local time on Saturday by drivers who saw two naked men fighting on a bike track next to the city's MacArthur Causeway.

When they arrived at the scene they drew their weapons and ordered the man to stop biting at the other man's face. He ignored them, prompting officers to open fire.

Even after being shot, the man continued and the officers fired again, killing him.

Police are still trying to work out what caused the confrontation that led to the shooting.

"During this confrontation an officer did discharge his weapon striking one of the individuals that individual has lost his life right now," said Detective Willie Moreno, spokesperson for Miami police.

The police refused to give full details on the record but sources have given graphic accounts to CBS news channel in Miami.

With the attacker dead, lying nude on the pavement, officers and paramedics were able to get to his victim and rush him to Jackson Memorial hospital. Police sources say the man had virtually no face and was unrecognisable.